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Abstract:

Provided are (1) a novel phenyl sulfonate compound, (2) a nonaqueous
electrolytic solution comprising an electrolyte salt dissolved in a
nonaqueous solvent and containing a phenyl sulfonate compound of the
following general formula (II) in an amount of from 0.01 to 10% by mass
of the nonaqueous electrolytic solution, and (3) a lithium battery
containing the nonaqueous electrolytic solution and excellent in
low-temperature cycle property.
##STR00001##
(wherein X1 to X5 each independently represents a fluorine atom
or a hydrogen atom, and from one to four of these are fluorine atoms;
R2 represents a linear or branched alkyl group having from 1 to 6
carbon atoms, a linear or branched alkyl group having from 1 to 6 carbon
atoms in which at least one hydrogen atom is substituted with a halogen
atom, or an aryl group having from 6 to 9 carbon atoms).

Claims:

1. A phenyl sulfonate compound represented by the following general
formula (I): ##STR00006## (wherein X1 to X5 each independently
represents a fluorine atom or a hydrogen atom, and from two to four of
these are fluorine atoms; R1 represents a linear or branched alkyl
group having from 1 to 6 carbon atoms, a linear or branched alkyl group
having from 1 to 6 carbon atoms in which at least one hydrogen atom is
substituted with a halogen atom, or an aryl group having from 6 to 9
carbon atoms).

2. A nonaqueous electrolytic solution comprising an electrolyte salt
dissolved in a nonaqueous solvent and containing a phenyl sulfonate
compound represented by the following general formula (II) in an amount
of from 0.01 to 10% by mass of the nonaqueous electrolytic solution:
##STR00007## (wherein X1 to X5 each independently represents a
fluorine atom or a hydrogen atom, and from one to four of these are
fluorine atoms; R2 represents a linear or branched alkyl group
having from 1 to 6 carbon atoms, a linear or branched alkyl group having
from 1 to 6 carbon atoms in which at least one hydrogen atom is
substituted with a halogen atom, or an aryl group having from 6 to 9
carbon atoms).

3. A lithium battery comprising a positive electrode, a negative electrode
and a nonaqueous electrolytic solution of an electrolyte salt dissolved
in a nonaqueous solvent, wherein the nonaqueous electrolytic solution
contains a phenyl sulfonate compound of the above-mentioned general
formula (II) in an amount of from 0.01 to 10% by mass of the nonaqueous
electrolytic solution.

Description:

TECHNICAL FIELD

[0001]The present invention relates to a phenyl sulfonate compound useful
as intermediate materials for medicines, agricultural chemicals,
electronic materials, polymer materials and the like, or as battery
materials, as well as to a nonaqueous electrolytic solution and a lithium
battery which is excellent in low-temperature cycle property.

BACKGROUND ART

[0002]In recent years, lithium secondary batteries have been widely used
as power supplies for electronic devices such as mobile telephones,
notebook-size personal computers and the like, and also as power supplies
for electric vehicles and for electric power storage, etc. These
electronic devices and vehicles may be used in a broad temperature range,
for example, at midsummer high temperatures or at frigid low
temperatures, and are therefore required to have an improved cycle
property in a broad temperature range.

[0003]A lithium secondary battery is mainly constituted of a positive
electrode and a negative electrode containing a material capable of
absorbing and releasing lithium, and a nonaqueous electrolytic solution
containing a lithium salt and a nonaqueous solvent. As the nonaqueous
solvent, used are carbonates such as ethylene carbonate (EC), propylene
carbonate (PC), etc.

[0004]As the negative electrode, known are metal lithium, and metal
compounds and carbon materials capable of absorbing and releasing
lithium. In particular, lithium secondary batteries using a carbon
material capable of absorbing and releasing lithium such as coke,
artificial graphite, natural graphite or the like have been widely put
into practical use.

[0005]It is known that, in the lithium secondary battery using a
highly-crystalline carbon material such as artificial graphite, natural
graphite or the like as the negative electrode material, the decomposed
product or gas generated through reductive decomposition of the solvent
in the nonaqueous electrolytic solution on the surface of the negative
electrode during charging detracts from the electrochemical reaction
favorable for the battery, therefore worsening the cycle property of the
battery. Deposition of the decomposed product of the nonaqueous solvent
interferes with smooth absorption and release of lithium by the negative
electrode, and therefore, in particular, the cycle property at low
temperatures may be thereby often worsened.

[0006]In addition, it is known that a lithium secondary battery using a
lithium metal or its alloy, or a metal elemental substance such as tin,
silicon or the like or its metal oxide as the negative electrode material
may have a high initial battery capacity but its battery performance such
as battery capacity and cycle property greatly worsens, since the
micronized powdering of the material is promoted during cycles thereby
bringing about accelerated reductive decomposition of the nonaqueous
solvent, as compared with the negative electrode of a carbon material. In
addition, the micronized powdering of the negative electrode material and
the deposition of the decomposed product of the nonaqueous solvent may
interfere with smooth absorption and release of lithium by the negative
electrode, and therefore, in particular, the cycle property at low
temperatures may be thereby often worsened.

[0007]On the other hand, it is known that, in a lithium secondary battery
using, for example, LiCoO2, LiMn2O4, LiNiO2,
LiFePO4 or the like as the positive electrode, when the nonaqueous
solvent in the nonaqueous electrolytic solution is heated at a high
temperature in the charged state, the decomposed product or gas thereby
locally generated through partial oxidative decomposition in the
interface between the positive electrode material and the nonaqueous
electrolytic solution interferes with the electrochemical reaction
favorable for the battery, and therefore the battery performance such as
cycle property is thereby also worsened.

[0008]As in the above, the decomposed product or gas generated through
decomposition of the nonaqueous electrolytic solution on the negative
electrode or the positive electrode interferes with the movement of
lithium ions or swells the battery, and the battery performance is
thereby worsened. Despite the situation, electronic appliances equipped
with lithium secondary batteries therein are offering more and more an
increasing range of functions and are being in a stream of further
increase in the power consumption. With that, the capacity of lithium
secondary batteries is being much increased, and the space volume for the
nonaqueous electrolytic solution in the battery is decreased by
increasing the density of the electrode and by reducing the useless space
volume in the battery. Accordingly, the situation is that even
decomposition of only a small amount of the nonaqueous electrolytic
solution may worsen the battery performance at low temperatures.

[0009]JP-A 11-162511 discloses a lithium secondary battery with a
nonaqueous electrolytic solution, which contains a compound having an
S--O bond as the organic solvent therein and in which the material of the
collector for the positive electrode and the material of the part of the
outer casing that is in contact with the electrolytic solution on the
positive electrode side is a valve metal or its alloy. In the paragraph
[0018] of the patent publication, a phenyl methanesulfonate compound as
an example of the compound having an S--O bond is disclosed, and the
battery capacity in the initial stage at 25° C. and the cycle
property are shown; however, the cycle property is not sufficiently
satisfactory.

[0010]As a lithium primary battery, for example, there is known a lithium
primary battery comprising manganese dioxide or graphite fluoride as the
positive electrode and a lithium metal as the negative electrode, and
this is widely used as having a high energy density. It is desired to
inhibit the increase in the internal resistance of the battery during
long-term storage and to improve the discharge load characteristic
thereof at room temperature or low temperatures.

[0011]Recently, further, as a novel power source for electric vehicles or
hybrid electric vehicles, electric storage devices have been developed,
for example, an electric double layer capacitor using activated carbon or
the like as the electrode from the viewpoint of the output power density
thereof, and a so-called hybrid capacitor comprising a combination of the
electric storage principle of a lithium ion secondary battery and that of
an electric double layer capacitor (both the capacity by lithium
absorption and release and the electric double layer capacity are
utilized) from the viewpoint of both the energy density and the output
power density thereof; and it is desired to improve the characteristics,
especially the low-temperature cycle property of these capacitors.

DISCLOSURE OF THE INVENTION

[0012]An object of the present invention is to provide a specific phenyl
sulfonate compound useful as intermediate materials for medicines,
agricultural chemicals, electronic materials, polymer materials and the
like, or as battery materials, and to provide a nonaqueous electrolytic
solution capable of improving the low-temperature cycle property, and a
lithium battery using it.

[0013]The present inventors have assiduously studied for the purpose of
solving the above-mentioned problems and, as a result, have found that,
in a nonaqueous electrolytic solution containing an electrolyte salt
dissolved in a nonaqueous solvent, when a phenyl sulfonate compound in
which the benzene ring has from 1 to 4 fluorine atoms and the oxygen atom
of the sulfonate group directly bonds to the benzene ring is added to the
nonaqueous electrolytic solution, then the low-temperature cycle property
can be improved, and have completed the present invention.

[0014]Specifically, the present invention provides the following (1) to
(3):

[0015](1) A phenyl sulfonate compound represented by the following general
formula (I):

##STR00002##

(wherein X1 to X5 each independently represents a fluorine atom
or a hydrogen atom, and from two to four of these are fluorine atoms;
R1 represents a linear or branched alkyl group having from 1 to 6
carbon atoms, a linear or branched alkyl group having from 1 to 6 carbon
atoms in which at least one hydrogen atom is substituted with a halogen
atom, or an aryl group having from 6 to 9 carbon atoms).

[0016](2) A nonaqueous electrolytic solution comprising an electrolyte
salt dissolved in a nonaqueous solvent and containing a phenyl sulfonate
compound represented by the following general formula (II) in an amount
of from 0.01 to 10% by mass of the nonaqueous electrolytic solution:

##STR00003##

(wherein X1 to X5 each independently represents a fluorine atom
or a hydrogen atom, and from one to four of these are fluorine atoms;
R2 represents a linear or branched alkyl group having from 1 to 6
carbon atoms, a linear or branched alkyl group having from 1 to 6 carbon
atoms in which at least one hydrogen atom is substituted with a halogen
atom, or an aryl group having from 6 to 9 carbon atoms).

[0017](3) A lithium battery comprising a positive electrode, a negative
electrode and a nonaqueous electrolytic solution of an electrolyte salt
dissolved in a nonaqueous solvent, wherein the nonaqueous electrolytic
solution contains a phenyl sulfonate compound of the above-mentioned
general formula (II) in an amount of from 0.01 to 10% by mass of the
nonaqueous electrolytic solution.

[0018]According to the present invention, there are provided a novel
phenyl sulfonate compound useful as intermediate materials for medicines,
agricultural chemicals, electronic materials, polymer materials and the
like, or as battery materials, a nonaqueous electrolytic solution capable
of improving the low-temperature cycle property, and a lithium battery
using it.

BRIEF DESCRIPTION OF THE DRAWING

[0019]FIG. 1 This is a graph showing the relationship between the number
of fluorine atoms on the benzene ring and the low-temperature cycle
property.

BEST MODE FOR CARRYING OUT THE INVENTION

Phenyl Sulfonate Compound

[0020]The phenyl sulfonate compound of the present invention is a novel
compound represented by the following general formula (I):

##STR00004##

[0021]In the general formula (I), X1 to X5 each independently
represents a fluorine atom or a hydrogen atom, and from two to four of
these are fluorine atoms; R1 represents a linear or branched alkyl
group having from 1 to 6 carbon atoms, a linear or branched alkyl group
having from 1 to 6 carbon atoms in which at least one hydrogen atom is
substituted with a halogen atom, or an aryl group having from 6 to 9
carbon atoms.

[0022]The linear or branched alkyl group having from 1 to 6 carbon atoms
for R1 in the general formula (I) includes a methyl group, an ethyl
group, an n-propyl group, an isopropyl group, an n-butyl group, an
isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group,
a neopentyl group, a sec-pentyl group, a tert-pentyl group, an n-hexyl
group, a 2-hexyl group, etc. The linear or branched alkyl group having
from 1 to 6 carbon atoms in which at least one hydrogen atom is
substituted with a halogen atom may be a substituent of the
above-mentioned alkyl group in which at least one hydrogen atom is
substituted with a halogen atom, and its concrete examples include a
trifluoromethyl group, and a 2,2,2-trifluoroethyl group.

[0023]The aryl group having from 6 to 9 carbon atoms for R1 in the
general formula (I) includes a phenyl group, a tosyl group, a mesityl
group, etc.

[0024]R1 in the general formula (I) is preferably a methyl group, an
ethyl group, a trifluoromethyl group or a phenyl group from the viewpoint
of the effect of the compound for improving the low-temperature cycle
property in using it in a nonaqueous electrolytic solution, more
preferably a methyl group.

[0026]Also preferred are phenyl sulfonate compounds corresponding to the
above in which R1 is an ethyl group, an n-propyl group, an isopropyl
group, an n-butyl group, an isobutyl group, a sec-butyl group, a
tert-butyl group, an n-pentyl group, a neopentyl group, a sec-pentyl
group, a tert-pentyl group, an n-hexyl group, a 2-hexyl group, etc.

Production of Phenyl Sulfonate Compound of General Formula (I)

[0027]The phenyl sulfonate compound, especially a fluorophenyl
alkanesulfonate compound represented by the general formula (I) may be
produced by reacting a fluorophenol compound with an alkanesulfonyl
halide or an alkanesulfonic acid anhydride for esterification in the
presence of a base in a solvent or in the absence of a solvent; however,
the production is not limited to the method.

[0031]The amount of the alkanesulfonyl halide or the alkanesulfonic acid
anhydride to be used is preferably from 0.9 to 10 mols, more preferably
from 1 to 3 mols, most preferably from 1 to 1.5 mols relative to 1 mol of
the fluorophenol compound.

[0032]The solvent to be used may be any one inert to the reaction, and is
not specifically defined. For example, it includes aliphatic hydrocarbons
such as hexane, heptane, etc.; halogenohydrocarbons such as
dichloroethane, dichloropropane, etc.; aromatic hydrocarbons such as
toluene, xylene, etc.; halogenoaromatic hydrocarbons such as
chlorobenzene, fluorobenzene, etc.; ethers such as diethyl ether, etc.;
nitriles such as acetonitrile, propionitrile, etc.; amides such as
N,N-dimethylformamide, etc.; sulfoxides such as dimethyl sulfoxide, etc.;
nitro compounds such as nitromethane, nitroethane, etc.; ketones such as
acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone,
etc.; esters such as ethyl acetate, dimethyl carbonate, etc.; water, and
their mixtures. Especially preferred are toluene, and xylene.

[0033]The amount of the solvent to be used is preferably from 0 to 30
parts by mass, more preferably from 1 to 15 parts by mass relative to 1
part by mass of the fluorophenol compound.

[0034]As the base, any of an inorganic base or an organic base may be used
herein.

[0037]One or more such bases may be used herein either singly or as
combined.

[0038]The amount of the base to be used is preferably from 0.8 to 5 mols,
more preferably from 1 to 3 mols, even more preferably from 1 to 1.5 mols
relative to 1 mol of the fluorophenol compound as the production of side
products can be prevented.

[0039]In the reaction of the fluorophenol compound and the alkanesulfonyl
halide or alkanesulfonic acid anhydride, the lowermost limit of the
reaction temperature is preferably -70° C. or higher, more
preferably -20° C. or higher in order not to lower the reactivity.
The uppermost limit of the reaction temperature is preferably 80°
C. or lower, more preferably 60° C. or lower in order to prevent
side reaction or prevent decomposition of the product.

[0040]The reaction time may depend on the reaction temperature and the
reactions scale; however, when the reaction time is too short, unreacted
substances may remain; but on the contrary, when the reaction time is too
long, then the product may decompose or side reaction may occur.
Therefore, the reaction time is preferably from 0.1 to 12 hours, more
preferably from 0.2 to 6 hours. The reaction pressure may fall within a
range of from 0.1 to 10 atm, preferably from 0.5 to 5 atm.

Nonaqueous Electrolytic Solution

[0041]The nonaqueous electrolytic solution of the present invention is a
nonaqueous electrolytic solution of an electrolyte salt dissolved in a
nonaqueous solvent, and is characterized by containing a phenylsulfonyl
compound represented by the following general formula (II) in an amount
of from 0.01 to 10% by mass of the nonaqueous electrolytic solution.

##STR00005##

[0042]In the general formula (II), X1 to X5 each independently
represents a fluorine atom or a hydrogen atom, and from one to four of
these are fluorine atoms; R2 represents a linear or branched alkyl
group having from 1 to 6 carbon atoms, a linear or branched alkyl group
having from 1 to 6 carbon atoms in which at least one hydrogen atom is
substituted with a halogen atom, or an aryl group having from 6 to 9
carbon atoms.

[0043]The linear or branched alkyl group having from 1 to 6 carbon atoms
for R2 in the general formula (II) includes a methyl group, an ethyl
group, an n-propyl group, an isopropyl group, an n-butyl group, an
isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group,
a neopentyl group, a sec-pentyl group, a tert-pentyl group, an n-hexyl
group, a 2-hexyl group, etc. The linear or branched alkyl group having
from 1 to 6 carbon atoms in which at least one hydrogen atom is
substituted with a halogen atom may be a substituent of the
above-mentioned alkyl group in which at least one hydrogen atom is
substituted with a halogen atom, and its concrete examples include a
trifluoromethyl group, and a 2,2,2-trifluoroethyl group.

[0044]The aryl group having from 6 to 9 carbon atoms for R2 in the
general formula (II) includes a phenyl group, a tosyl group, a mesityl
group, etc.

[0045]R2 in the general formula (II) is preferably a methyl group, an
ethyl group, a trifluoromethyl group or a phenyl group from the viewpoint
of the effect of the compound for improving the low-temperature cycle
property, more preferably a methyl group.

[0047]Also preferred are phenyl sulfonate compounds corresponding to the
above in which R2 is an ethyl group, an n-propyl group, an isopropyl
group, an n-butyl group, an isobutyl group, a sec-butyl group, a
tert-butyl group, an n-pentyl group, a neopentyl group, a sec-pentyl
group, a tert-pentyl group, an n-hexyl group, or a 2-hexyl group.

[0048]The phenyl sulfonate compound, especially a fluorophenyl
alkanesulfonate compound represented by the general formula (II) may be
produced by reacting a fluorophenol compound with an alkanesulfonyl
halide or an alkanesulfonic acid anhydride for esterification in the
presence of a base in a solvent or in the absence of a solvent, like in
the production method for the phenyl sulfonate compound of the general
formula (I). Its concrete example and preferred example are the same as
above, and describing them herein is omitted. In this case, as the
fluorophenol compound, also usable are 2-fluorophenol, 3-fluorophenol,
4-fluorophenol, etc., in addition to the above-exemplified ones.

[0049]The compound of the general formula (II) where from one to four of
X1 to X5 are fluorine atoms can improve the low-temperature
cycle property, and its reason may be considered as follows:
Specifically, decomposition of the phenyl sulfonate compound of the
present invention can induce a fluorine atom-containing, stable surface
film on a negative electrode, and therefore the solvent in the nonaqueous
electrolytic solution is prevented from being decomposed. At the same
time, in particular, when the compound has one or two fluorine atoms, the
polymerization of the benzene ring is not promoted too excessively even
when the fluorine atoms are released through the decomposition of the
phenyl sulfonate compound, and therefore, a flexible surface film can be
formed on the negative electrode. Accordingly, absorption and release of
lithium ions at low temperatures could be effected smoothly, and the
low-temperature cycle property can be significantly improved.

[0050]When the compound has two fluorine atoms on the benzene ring, its
effect of improving the low-temperature cycle property is the highest.
With the increase in the number of the fluorine atoms on the benzene
ring, the polymerization of the benzene ring is promoted more, and
therefore, the surface film on the negative electrode may be rigid and
the effect of the compound for improving the low-temperature cycle
property may be lower. Accordingly, the number of the fluorine atoms is
preferably at most 4. Specifically, the number of the fluorine atoms on
the benzene ring in the general formula (II) is most preferably 2, but
next to it, the benzene ring preferably has one fluorine, and further
next to it, the benzene ring has three fluorine atoms.

[0051]The effect of the compound for improving the low-temperature cycle
property may depend on the position of the fluorine atom therein. When
the compound has a fluorine atom at the ortho-position and the
para-position, then it is preferred as the compound well improves the
low-temperature cycle property, and more preferably, the compound has a
fluorine atom at the para-position.

[0052]In the nonaqueous electrolytic solution of the present invention,
the effect for improving the low-temperature cycle property by the phenyl
sulfonate compound of the general formula (II) is an effect peculiar to
the compound having a sulfone group with an oxygen atom directly bonding
to the benzene ring, or that is having a sulfonyloxy group directly
bonding thereto.

[0053]For example, a benzenesulfonate in which the sulfur atom directly
bonds to the benzene ring, or a benzenesulfonate with a carbon atom
directly bonding to the benzene ring has no effect for improving the
low-temperature cycle property. Though not always clear, the reason may
be considered as follows: The phenyl sulfonate compound with an oxygen
atom directly bonding to the benzene ring may form a surface film having
an oxygen atom bonding to the benzene ring on the electrode, therefore
expressing the effect of smoothly moving lithium ions.

[0054]Regarding the amount of the compound of the general formula (II) in
the nonaqueous electrolytic solution of the present invention, when the
amount is more than 10% by mass, then the surface film may be formed too
excessively on the electrode and therefore, the low-temperature cycle
property may be rather worsened; but when the amount is less than 0.01%
by mass, the surface film could not be formed sufficiently, and therefore
the compound would be ineffective for improving the low-temperature cycle
property. Accordingly, the content of the compound is at least 0.01% by
mass of the nonaqueous electrolytic solution (that is, the content of the
compound is at least 0.01% by mass relative to the mass of the nonaqueous
electrolytic solution), preferably at least 0.1% by mass, more preferably
at least 0.2% by mass, even more preferably at least 0.3% by mass. Its
uppermost limit is at most 10% by mass, preferably at most 7% by mass,
more preferably at most 5% by mass, even more preferably at most 3% by
mass.

[0055]In the nonaqueous electrolytic solution of the present invention,
the compound of the general formula (II) can exhibit its effect of
improving the low-temperature cycle property even when used alone in the
solution, but when combined with any of a nonaqueous solvent, an
electrolyte salt and further other additives to be mentioned below, the
compound exhibits a specific effect of synergistically improving the
low-temperature cycle property. Though not always clear, the reason may
be considered because a mixed surface film having a high ionic
conductivity, which contains the fluorine of the compound of the general
formula (II) and contains an element different from fluorine, is formed
whereby the solvent in the nonaqueous electrolytic solution can be more
effectively prevented from being decomposed on the electrode surface of
the positive and negative electrodes.

[0057]The cyclic carbonates include ethylene carbonate (EC), propylene
carbonate (PC), butylene carbonate (BC), 4-fluoro-1,3-dioxolan-2-one
(FEC), trans or cis-4,5-difluoro-1,3-dioxolan-2-one (hereinafter the two
are collectively referred to as "DFEC"), vinylene carbonate (VC),
vinylethylene carbonate (VEC), etc. Of those cyclic carbonates, FEC, VC
and VEC are preferred as the cycle property can be improved; and PC is
preferred as the low-temperature cycle property can be improved. In
general, FEC, DFEC, VC and VEC may worsen the low-temperature cycle
property, but the nonaqueous electrolytic solution containing any of
these along with the sulfone compound of the present invention may have
improved low-temperature cycle property.

[0058]One type of those solvents may be used, but using two or more
different types as combined is preferred as further improving the
low-temperature cycle property. Preferred combinations of the cyclic
carbonates include EC and PC; EC and VC; PC and VC; FEC and VC; FEC and
EC; FEC and PC; DFEC and EC; DFEC and PC; DFEC and VC; DFEC and VEC; etc.
Of these combinations, more preferred are EC and VC; FEC and PC; and DFEC
and PC.

[0059]Not specifically defined, the content of the cyclic carbonate is
preferably from 10 to 40% by volume relative to the total volume of the
nonaqueous solvent. When the content is less than 10% by volume, then the
conductivity of the nonaqueous electrolytic solution may lower; but when
more than 40% by volume, then the viscosity of the nonaqueous
electrolytic solution may increase and the low-temperature cycle property
may worsen. Accordingly, the above range is preferred.

[0060]The linear carbonates include asymmetric linear carbonates such as
methyl ethyl carbonate (MEC), methyl propyl carbonate, methyl isopropyl
carbonate, methyl butyl carbonate, ethyl propyl carbonate, etc.;
symmetric linear carbonates such as dimethyl carbonate(DMC), diethyl
carbonate (DEC), dipropyl carbonate, dibutyl carbonate, etc. In
particular, the asymmetric carbonates are preferred, as effectively
improving the low-temperature cycle property. One type of those solvents
may be used, but using two or more different types as combined is
preferred as further improving the low-temperature cycle property.

[0061]Not specifically defined, the content of the linear carbonate is
preferably from 60 to 90% by volume relative to the total volume of the
nonaqueous solvent. When the content is less than 60% by volume, then the
viscosity of the nonaqueous electrolytic solution may increase; but when
more than 90% by volume, then the electric conductivity of the nonaqueous
electrolytic solution may lower and the low-temperature cycle property
may worsen. Accordingly, the above range is preferred.

[0065]In general, the S═O bond-containing compounds may worsen the
low-temperature cycle property; however, when using them as combined with
the phenyl sulfonate compound of the present invention is favorable as
improving the low-temperature cycle property. Regarding the content of
the S═O bond-containing compound except the phenyl sulfonate compound
of the present invention, when the content thereof is more than 10% by
mass of the nonaqueous electrolytic solution, then the low-temperature
cycle property may worsen; but when less than 0.01% by mass, the effect
of improving the low-temperature cycle property could not be sufficiently
attained. Accordingly, the content of the S═O bond-containing
compound is preferably at least 0.01% by mass of the nonaqueous
electrolytic solution, more preferably at least 0.1% by mass, even more
preferably at least 0.5% by mass. The uppermost limit of the content is
preferably at most 10% by mass, more preferably at most 5% by mass, even
more preferably at most 3% by mass.

[0066]In general, the nonaqueous solvents are used as a mixture thereof
for attaining the suitable physical properties. Regarding their
combinations, for example, there are mentioned a combination of a cyclic
carbonate and a linear carbonate, a combination of a cyclic carbonate, a
linear carbonate and a lactone, a combination of a cyclic carbonate, a
linear carbonate and an ether, a combination of a cyclic carbonate, a
linear carbonate and a linear ester, a combination of a cyclic carbonate,
a linear carbonate and a nitrile, a combination of a cyclic carbonate, a
linear carbonate and the above-mentioned S═O bond-containing
compound, etc.

[0067]Of those, preferred is using a nonaqueous solvent of a combination
of at least a cyclic carbonate and a linear carbonate, as effectively
improving the low-temperature cycle property. The ratio of the cyclic
carbonate to the linear carbonate is not specifically defined.
Preferably, the ratio (by volume) of cyclic carbonate/linear carbonate is
from 10/90 to 40/60, more preferably from 15/85 to 35/65, even more
preferably from 20/80 to 30/70.

Electrolyte Salt

[0068]The electrolyte salt for use in the nonaqueous electrolytic solution
of the present invention includes Li salts such as LiPF6,
LiBF4, LiClO4, etc.; linear alkyl group-having lithium salts
such as LiN(SO2CF3)2, LiN(SO2C2F5)2,
LiCF3SO3, LiC(SO2CF3)3,
LiPF4(CF3)2, LiPF3(C2F5)3,
LiPF3(CF3)3, LiPF3(iso-C3F7)3,
LiPF5(iso-C3F7), etc.; cyclic alkylene chain-having
lithium salts such as (CF2)2(SO2)2NLi,
(CF2)3(SO2)2NLi, etc.; and lithium salts with an
anion of an oxalate complex such as lithium bis[oxalate-O,O']borate,
lithium difluoro[oxalate-O,O']borate, etc. Of those, especially preferred
electrolyte salts are LiPF6, LiBF4,
LiN(SO2CF3)2, LiN(SO2C2F5)2; and most
preferred electrolyte salts are LiPF6, LiBF4 and
LiN(SO2CF3)2. One or more of these electrolyte salts may
be used herein either singly or as combined.

[0069]A preferred combination of these electrolyte salts is a combination
containing LiPF6 as combined with at least one selected from
LiBF4, LiN(SO2CF3)2 and
LiN(SO2C2F5)2. Preferred are a combination of
LiPF6 and LiBF4; a combination of LiPF6 and
LiN(SO2CF3)2; a combination of LiPF6 and
LiN(SO2C2F5)2, etc.

[0070]When the ratio (by mol) of LiPF6/[LiBF4 or
LiN(SO2CF3)2 or LiN(SO2C2F5)2] is
smaller than 70/30 in point of the proportion of LiPF6, or when the
ratio is larger than 99/1 in point of the proportion of LiPF6, then
the low-temperature cycle property may worsen. Accordingly, the ratio (by
mol) of LiPF6/[LiBF4 or LiN(SO2CF3)2 or
LiN(SO2C2F5)2] is preferably within a range of from
70/30 to 99/1, more preferably from 80/20 to 98/2. The combination
falling within the above range is more effective for bettering the
low-temperature cycle property.

[0071]The electrolyte salts may be combined in any desired ratio. In the
combination of LiPF6 with any of LiBF4,
LiN(SO2CF3)2 and LiN(SO2C2F5)2, when
the proportion (as molar fraction) of the other electrolyte salt than
those ingredients to the total electrolyte salts is less than 0.01%, then
the effect of improving the low-temperature cycle property may be poor;
but when it is more than 45%, then the low-temperature cycle property may
worsen. Accordingly, the proportion (as molar fraction) is preferably
from 0.01 to 45%, more preferably from 0.03 to 20%., even more preferably
from 0.05 to 10%, most preferably from 0.05 to 5%.

[0072]The concentration of all these electrolyte salts as dissolved in the
solution is generally preferably at least 0.3 M relative to the
above-mentioned nonaqueous solvent, more preferably at least 0.5 M, most
preferably at least 0.7 M. The uppermost limit of the concentration is
preferably at most 2.5 M, more preferably at most 2.0 M, even more
preferably at most 1.5 M.

[0074]An aromatic compound may be added to the nonaqueous electrolytic
solution of the present invention, thereby securing the safety of the
battery in overcharging. Preferred examples of the aromatic compound
include cyclohexylbenzene, fluorocyclohexylbenzene compound
(1-fluoro-2-cyclohexylbenzene, 1-fluoro-3-cyclohexylbenzene,
1-fluoro-4-cyclohexylbenzene), tert-butylbenzene, tert-amylbenzene,
1-fluoro-4-tert-butylbenzene, 1,3-di-tert-butylbenzene, biphenyl,
terphenyl (o-, m-, p-form), diphenyl ether, fluorobenzene,
difluorobenzene (o-, m-, p-form), 2,4-difluoroanisole, partially
hydrogenated (1,2-dicyclohexylbenzene, 2-phenylbicyclohexyl,
1,2-diphenylcyclohexane, o-cyclohexylbiphenyl), etc. One or more of these
compounds may be used herein either singly or as combined.

Production of Nonaqueous Electrolytic Solution

[0075]The nonaqueous electrolytic solution of the present invention can be
produced, for example, by mixing the above-mentioned nonaqueous solvents
followed by dissolving therein the above-mentioned electrolyte salt and
the compound of the general formula (II) in an amount of from 0.01 to 10%
by mass of the resulting nonaqueous electrolytic solution.

[0076]In this case, the compounds to be added to the nonaqueous solvent
and the electrolytic solution are preferably previously purified within a
range not significantly detracting from the producibility, in which,
therefore, the impurity content is preferably as low as possible.

[0077]For example, air or carbon dioxide may be incorporated into the
nonaqueous electrolytic solution of the present invention to thereby
prevent gas generation resulting from decomposition of the electrolytic
solution and to enhance the battery characteristics such as the long-term
cycle property and the charge storage property in the charged state.

[0078]In the present invention, from the viewpoint of improving the
charging and discharging characteristics at high temperatures, the
nonaqueous electrolytic solution preferably contains carbon dioxide as
dissolved therein. The amount of carbon dioxide to be dissolved in the
nonaqueous electrolytic solution is preferably at least 0.001 by mass of
the solution, more preferably at least 0.05% by mass, even more
preferably at least 0.2% by mass; and most preferably, carbon dioxide is
dissolved in the nonaqueous electrolytic solution until its saturation
therein.

[0079]The nonaqueous electrolytic solution of the present invention is
favorably used for the electrolytic solution for lithium primary
batteries and lithium secondary batteries. Further, the nonaqueous
electrolytic solution of the present invention is also usable as an
electrolytic solution for electric double layer capacitors or as an
electrolytic solution for hybrid capacitors. Of those, the nonaqueous
electrolytic solution of the present invention is most favorable for
lithium secondary batteries.

Lithium Battery

[0080]The lithium battery of the present invention collectively includes a
lithium primary battery and a lithium secondary battery, comprising a
positive electrode, a negative electrode and the above-mentioned
nonaqueous electrolytic solution of an electrolyte salt dissolved in a
nonaqueous solvent, and is characterized in that a phenyl sulfonate
compound of the above-mentioned general formula (II) is in the nonaqueous
electrolytic solution in an amount of from 0.01 to 10% by mass of the
nonaqueous electrolytic solution.

[0081]In the lithium battery of the present invention, the other
constitutive components such as a positive electrode and a negative
electrode except for the nonaqueous electrolytic solution can be used
with no limitation.

[0082]For example, as the positive electrode active material for lithium
secondary battery, usable are complex metal oxides of lithium containing
any of cobalt, manganese or nickel. One or more such positive electrode
active materials may be used either singly or as combined.

[0084]For enhancing the safety in overcharging or enhancing the cycle
property, the lithium complex oxide may be partly substituted with any
other element for enabling the use of the battery at a charging potential
of 4.3 V or more. For example, a part of cobalt, manganese and nickel may
be substituted with at least one element of Sn, Mg, Fe, Ti, Al, Zr, Cr,
V, Ga, Zn, Cu, Bi, Mo, La, etc.; or O may be partly substituted with S or
F; or the oxide may be coated with a compound containing such other
element.

[0085]Of those, preferred are lithium complex metal oxides such as
LiCoO2, LiMn2O4 and LiNiO2, with which the positive
electrode charging potential in a full-charging state may be 4.3 V or
more, based on Li. More preferred are lithium complex oxides usable at
4.4 V or more, such as LiCO1-xMxO2 (where M is at least
one element of Sn, Mg, Fe, Ti, Al, Zr, Cr, V, Ga, Zn and Cu;
0.001≦x≦0.05), LiCO1/3Ni1/3Mn1/3O2, and
LiNi1/2Mn3/2O4.

[0087]The lithium-containing olivine-type phosphates may be partly
substituted with any other element. For example, a part of iron, cobalt,
nickel and manganese therein may be substituted with at least one element
selected from Co, Mn, Ni, Mg, Al, B, Ti, V, Nb, Cu, Zn, Mo, Ca, Sr, W and
Zr; or the phosphates may be coated with a compound containing any of
these other elements or with a carbon material. Of those, preferred are
LiFePO4 and LiMnPO4.

[0090]Not specifically defined, the electroconductive agent of the
positive electrode may be any electron-transmitting material not
undergoing chemical change. For example, it includes graphites such as
natural graphite (flaky graphite, etc.), artificial graphite, etc.;
carbon blacks such as acetylene black, Ketjen black, channel black,
furnace black, lamp black, thermal black, etc. Graphites and carbon
blacks may be combined suitably. The amount of the electroconductive
agent to be added to the positive electrode mixture is preferably from 1
to 10% by mass, more preferably from 2 to 5% by mass.

[0091]The positive electrode may be formed by mixing the above-mentioned
positive electrode active material with an electroconductive agent such
as acetylene black, carbon black or the like, and with a binder such as
polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF),
styrene/butadiene copolymer (SBR), acrylonitrile/butadiene copolymer
(NBR), carboxymethyl cellulose (CMC), ethylene/propylene/diene terpolymer
or the like, then adding thereto a high-boiling-point solvent such as
1-methyl-2-pyrrolidone or the like, and kneading them to give a positive
electrode mixture, thereafter applying the positive electrode mixture
onto an aluminium foil or a stainless lath plate or the like serving as a
collector, and drying and shaping it under pressure, and then
heat-treating it in vacuum at a temperature of from 50° C. to
250° C. or so for about 2 hours.

[0092]The density of the part except the collector of the positive
electrode may be generally at least 1.5 g/cm3, and for further
increasing the capacity of the battery, the density is preferably at
least 2 g/cm3, more preferably at least 3 g/cm3, even more
preferably at least 3.6 g/cm3.

[0093]As the negative electrode active material for lithium secondary
battery, usable are one or more of lithium metal, lithium alloys, carbon
materials [graphites such as artificial graphite, natural graphite,
etc.;] and metal compounds capable of absorbing and releasing lithium,
either singly or as combined.

[0094]Of those, preferred are high-crystalline carbon materials such as
artificial graphite, natural graphite or the like of which the ability of
absorbing and releasing lithium ions is good. More preferred is a carbon
material having a graphite-type crystal structure where the lattice (002)
spacing (d002) is at most 0.340 nm (nanometers), especially from
0.335 to 0.337 nm. More preferably, the high-crystalline carbon material
is coated with a low-crystalline carbon material, as capable of improving
the low-temperature cycle property. When such a high-crystalline carbon
material is used, then it may react with a nonaqueous electrolytic
solution in charging thereby worsening the low-temperature cycle
property; however, in the lithium secondary battery of the present
invention, the reaction with the nonaqueous electrolytic solution can be
retarded.

[0095]The metal compound capable of absorbing and releasing lithium,
serving as a negative electrode active material, includes compounds
containing at least one metal element of Si, Ge, Sn, Pb, P, Sb, Bi, Al,
Ga, In, Ti, Mn, Fe, Co, Ni, Cu, Zn, Ag, Mg, Sr, Ba, etc. These metal
compounds may have any morphology of simple substances, alloys, oxides,
nitrides, sulfides, borides, alloys with lithium or the like; but
preferred are any of simple substances, alloys, oxides and alloys with
lithium, as capable of increasing the battery capacity. Above all, more
preferred are those containing at least one element selected from Si, Ge
and Sn, and even more preferred are those containing at least one element
selected from Si and Sn, as capable of increasing the capacity of the
battery.

[0096]The negative electrode may be formed, using the same
electroconductive agent, binder and high-boiling point solvent as in the
formation of the above-mentioned positive electrode. These are mixed and
kneaded to give a negative electrode mixture, then the negative electrode
mixture is applied onto a copper foil or the like serving as a collector,
then dried and shaped under pressure, and thereafter heat-treated in
vacuum at a temperature of from 50° C. to 250° C. or so for
about 2 hours.

[0097]As the negative electrode active material for lithium primary
battery, usable is a lithium metal or a lithium alloy.

[0098]In case where graphite is used as the negative electrode active
material, the density of the part except the collector of the negative
electrode may be generally at least 1.4 g/cm3, and for further
increasing the capacity of the battery, the density is preferably at
least 1.6 g/cm3, more preferably at least 1.7 g/cm3.

[0099]As the separator for battery, usable is a single-layer or laminate
porous film of polyolefin such as polypropylene, polyethylene or the
like, as well as a woven fabric, a nonwoven fabric, etc.

[0100]The structure of the lithium secondary battery is not specifically
defined. The battery may be a coin-shaped battery, a cylindrical battery,
a square-shaped battery, or a laminate-type battery, each having a single
layered or multi-layered separator.

[0101]The lithium secondary battery of the present invention exhibits
excellent long-term cycle property even when the final charging voltage
is 4.2 V or higher and particularly 4.3 V or higher. Furthermore, the
cycle property is good even when the final charging voltage is 4.4 V. The
final discharging voltage can be 2.5 V or more and further 2.8 V or more.
Not specifically defined, the current value may be generally within a
range of from 0.1 to 3 C. The lithium secondary battery of the present
invention may be charged and discharged at -40° C. to 100°
C. and preferably at 0° C. to 80° C.

[0102]In the present invention, as a countermeasure against the increase
in the internal pressure of the lithium secondary battery, there may be
employed a method of providing a safety valve in the battery cap or a
method of forming a cutout in the battery component such as the battery
can, the gasket or the like. In addition, as a safety countermeasure
against overcharging, a current breaker capable of detecting the internal
pressure of the battery to cut off the current may be provided in the
battery cap.

EXAMPLES

[0103]Production Example for the phenyl sulfonate compound of the present
invention, and Examples of an electrolytic solution using it are shown
below; however, the present invention should not be restricted by these
Examples.

Production Example

Production of 2,4-difluorophenyl methanesulfonate

[0104]10.00 g (0.077 mol) of 2,4-difluorophenol, 100 mL of toluene and
8.17 g (0.081 mol) of triethylamine were mixed at 25° C., and with
controlling the temperature of the reaction liquid to be at 20° C.
or lower in an ice bath, 9.24 g (0.081 mol) of methanesulfonyl chloride
was dropwise added thereto, taking 15 minutes, and these were reacted
with stirring at 25° C. for 1 hour. Water was added to the
reaction liquid to separate the organic layer, and the organic layer was
washed twice with saturated sodium bicarbonate water and once with water,
then dried with anhydrous MgSO4 and subjected to distillation under
reduced pressure (98° C./3 Torr) to give 15.1 g of
2,4-difluorophenyl methanesulfonate (yield 94%).

[0109]LiPF6 to be 1 M was dissolved in a nonaqueous solvent of
EC/MEC/DMC=30/35/35 (ratio by volume), and further 2,4-difluorophenyl
methanesulfonate was added thereto to prepare a nonaqueous electrolytic
solution, in an amount of 0.1% by mass of the resulting nonaqueous
electrolytic solution (Example 1),1% by mass (Example 2),5% by mass
(Example 3) and 10% by mass (Example 4).

Production of Lithium Ion Secondary Battery

[0110]93% by mass of LiCO0.98Mg0.02)2 (positive electrode
active material) and 3% by mass of acetylene black (electroconductive
agent) were mixed, and added to and mixed with a solution previously
prepared by dissolving 4% by mass of polyvinylidene fluoride (binder) in
1-methyl-2-pyrrolidone, thereby preparing a positive electrode mixture
paste. The positive electrode mixture paste was applied onto both
surfaces of an aluminium foil (collector), dried, processed under
pressure and cut into a predetermined size, thereby producing a long
rectangular, positive electrode sheet. The density of a part of the
positive electrode except the collector was 3.6 g/cm3.

[0111]95% by mass of artificial graphite (d002=0.335 nm, negative
electrode active material) coated with low-crystalline carbon was added
to and mixed with a solution previously prepared by dissolving 5% by mass
of polyvinylidene fluoride (binder) in 1-methyl-2-pyrrolidone, thereby
preparing a negative electrode mixture paste. The negative electrode
mixture paste was applied onto both surfaces of a copper foil
(collector), dried, processed under pressure and cut into a predetermined
size, thereby producing a long rectangular, negative electrode sheet. The
density of a part of the negative electrode except the collector was 1.7
g/cm3.

[0112]The positive electrode sheet, a porous polyethylene film separator,
the negative electrode sheet and a separator were laminated in that
order, and the resulting laminate was coiled up. The coil was housed into
a nickel-plated, iron-made cylindrical battery can serving also as a
negative electrode terminal. Further, the nonaqueous electrolytic
solution was injected thereinto, and the can was calked with a battery
cap having a positive electrode terminal, via a gasket therebetween,
thereby constructing a 18650-type cylindrical battery. The positive
electrode terminal was connected to the positive electrode sheet via an
aluminium lead tab therebetween; and the negative electrode can was
previously connected to the negative electrode sheet inside the battery,
via a nickel lead tab therebetween.

(2) Evaluation of Low-Temperature Cycle Property

[0113]In a thermostat chamber kept at 25° C., the battery
constructed as in the above was charged up to 4.2 V (charging final
voltage) with a constant current of 1 C, then charged for 2.5 hours at
the constant voltage of 4.2 V, and thereafter this was discharged under a
constant current of 1 C to a discharge voltage of 3.0 V (discharging
final voltage). Next, in a thermostat chamber kept at 0° C., this
was charged up to 4.2 V with a constant current of 1 C, then charged for
2.5 hours at the constant voltage of 4.2 V, and thereafter this was
discharged under a constant current of 1 C to a discharge voltage of 3.0
V. This is one cycle. The battery was subjected to 50 cycles.

[0114]After 50 cycles at 0° C., the discharge capacity retention
rate of the battery was determined according to the following formula,
and the results are shown in Table 1.

[0116]Cylindrical batteries were produced in the same manner as in Example
1, for which, however, LiPF6 to be 1 M was dissolved in a nonaqueous
solvent of EC/MEC/DMC=30/35/35 (ratio by volume), and further, in place
of adding 2,4-difluorophenyl methanesulfonate, 2-fluorophenyl
methanesulfonate (Example 5), 3-fluorophenyl methanesulfonate (Example
6), 4-fluorophenyl methanesulfonate (Example 7), 3,4-difluorophenyl
methanesulfonate (Example 8), 3,5-difluorophenyl methanesulfonate
(Example 9), 2,3,4-trifluorophenyl methanesulfonate (Example 10),
3,4,5-trifluorophenyl methanesulfonate (Example 11) or
2,3,5,6-tetrafluorophenyl methanesulfonate (Example 12) was added thereto
to prepare a nonaqueous electrolytic solution, in an amount of 1% by mass
of the resulting nonaqueous electrolytic solution; and the batteries were
evaluated. The results are shown in Table 1.

Example 13

[0117]A cylindrical battery was produced in the same manner as in Example
1, for which, however, LiPF6 to be 1 M was dissolved in a nonaqueous
solvent of EC/MEC/DMC=30/35/35 (ratio by volume), and further, 1% by mass
of 2,4-difluorophenyl methanesulfonate and 2% by mass of
1,3-propanesultone, relative to the resulting nonaqueous electrolytic
solution, were added thereto to prepare a nonaqueous electrolytic
solution, and the battery was evaluated. The result is shown in Table 1.

Example 14

[0118]A cylindrical battery was produced in the same manner as in Example
1, for which, however, LiPF6 to be 1 M was dissolved in a nonaqueous
solvent of EC/MEC/DMC=30/35/35 (ratio by volume), and further, 1% by mass
of 2,4-difluorophenyl methanesulfonate and 0.5% by mass of ethylene
sulfite, relative to the resulting nonaqueous electrolytic solution, were
added thereto to prepare a nonaqueous electrolytic solution, and the
battery was evaluated. The result is shown in Table 1.

Example 15

[0119]A cylindrical battery was produced in the same manner as in Example
1, for which, however, LiPF6 to be 0.95 M and LiN(SO2
CF3)2 to be 0.05 M were dissolved in a nonaqueous solvent of
EC/VC/MEC/DEC=28/2/35/35 (ratio by volume), and further, 1% by mass of
2,4-difluorophenyl methanesulfonate and 0.5% by mass of divinyl sulfone,
relative to the resulting nonaqueous electrolytic solution, were added
thereto to prepare a nonaqueous electrolytic solution, and the battery
was evaluated. The result is shown in Table 1.

Example 16

[0120]A cylindrical battery was produced in the same manner as in Example
1, for which, however, LiPF6 to be 0.95 M and LiBF4 to be 0.05
M were dissolved in a nonaqueous solvent of FEC/PC/DMC/DEC=20/10/35/35
(ratio by volume), and further, 1% by mass of 2,4-difluorophenyl
methanesulfonate, relative to the resulting nonaqueous electrolytic
solution, was added thereto to prepare a nonaqueous electrolytic
solution, and the battery was evaluated. The result is shown in Table 1.

Comparative Example 1

[0121]A cylindrical battery was produced in the same manner as in Example
1, for which, however, LiPF6 to be 1 M was dissolved in a nonaqueous
solvent of EC/MEC/DMC=30/35/35 (ratio by volume), but 2,4-difluorophenyl
methanesulfonate was not added thereto to prepare a nonaqueous
electrolytic solution, and the battery was evaluated. The result is shown
in Table 1.

Comparative Examples 2 to 4

[0122]Cylindrical batteries were produced in the same manner as in Example
1, for which, however, LiPF6 to be 1 M was dissolved in a nonaqueous
solvent of EC/MEC/DMC=30/35/35 (ratio by volume), and further, phenyl
methanesulfonate (Comparative Example 2), methyl
2,4-difluorobenzenesulfonate (Comparative Example 3), or methyl
2,4-difluorobenzoate (Comparative Example 4) was added thereto, in place
of adding 2,4-difluorophenyl methanesulfonate thereto, in an amount of 1%
by mass of the resulting nonaqueous electrolytic solution; and the
batteries were evaluated. The results are shown in Table 1.

[0123]As in Table 1, the lithium secondary batteries of Examples 1 to 16
have improved low-temperature cycle property, as compared with the
lithium secondary battery in Comparative Example 1 in which the phenyl
sulfonate compound of the present invention was not added, that in
Comparative Example 2 in which phenyl methanesulfonate with no fluorine
atom on the benzene ring was added, that in Comparative Example 3 in
which methyl 2,4-difluorobenzenesulfonate containing two fluorine atoms
on the benzene ring and having the sulfonate ester group directly bonding
to the benzene ring via the sulfur atom was added, and that in
Comparative Example 4 in which methyl 2,4-difluorobenzoate containing two
fluorine atoms on the benzene ring and having the ester group directly
bonding to the benzene ring via the carbon atom. Accordingly, it is known
that adding a phenyl sulfonate compound of the general formula (II) to a
nonaqueous electrolytic solution of an electrolyte salt dissolved in a
nonaqueous solvent brings about the unexpected specific effect.

[0124]FIG. 1 shows the relationship between the number of fluorine atoms
on the benzene ring and the low-temperature cycle property. When the
number of the fluorine atoms is one or two, the low-temperature cycle
property is especially good; and with the increase in the number of the
fluorine atoms more than two, the low-temperature cycle property tended
to gradually worsen. Accordingly, the number of the fluorine atoms on the
benzene ring is preferably from 1 to 4.

Example 17

[0125]A positive electrode sheet was produced, using LiFePO4
(positive electrode active material) in place of the positive electrode
active material used in Example 2.90% by mass of LiFePO4 and 5% by
mass of acetylene black (electroconductive agent) were mixed, and added
to and mixed with a solution previously prepared by dissolving 5% by mass
of polyvinylidene fluoride (binder) in 1-methyl-2-pyrrolidone, thereby
preparing a positive electrode mixture paste. A cylindrical battery was
produced and evaluated in the same manner as in Example 2, for which,
however, the positive electrode mixture paste was applied onto an
aluminium foil (collector), dried, processed under pressure and cut into
a predetermined size, thereby producing a long rectangular, positive
electrode sheet, and the final charging voltage was 3.6 V and the final
discharging voltage was 2.0 V. The result is shown in Table 2.

Comparative Example 5

[0126]A cylindrical battery was produced in the same manner as in Example
17, for which, however, 2,4-difluorophenyl methanesulfonate was not added
to the nonaqueous electrolytic solution; and the battery was evaluated.
The result is shown in Table 2.

Example 18

[0127]A negative electrode sheet was produced, using Si (negative
electrode active material) in place of the negative electrode active
material used in Example 1.80% by mass of Si and 15% by mass of acetylene
black (electroconductive agent) were mixed, and added to and mixed with a
solution previously prepared by dissolving 5% by mass of polyvinylidene
fluoride (binder) in 1-methyl-2-pyrrolidone, thereby preparing a negative
electrode mixture paste. A cylindrical battery was produced in the same
manner as in Example 2, for which, however, the negative electrode
mixture paste was applied onto a copper foil (collector), dried,
processed under pressure and cut into a predetermined size, thereby
producing a long rectangular, negative electrode sheet; and the battery
was evaluated. The result is shown Table 2.

Comparative Example 6

[0128]A cylindrical battery was produced in the same manner as in Example
18, for which, however, 2,4-difluorophenyl methanesulfonate was not added
to the nonaqueous electrolytic solution; and the battery was evaluated.
The result is shown Table 2.

[0129]In Table 2, from comparison between Example 17 and Comparative
Example 5 and comparison between Example 18 and Comparative Example 6, it
is known that adding a phenyl sulfonate compound of the general formula
(II) to the case of using a lithium-containing olivine-type iron
phosphate for the positive electrode and to the case of using Si for the
negative electrode also brings about the unexpected specific effect.
Accordingly, it is obvious that the effect of the present invention does
not depend on a specific positive electrode or negative electrode.

[0130]Further, the nonaqueous electrolytic solution of the present
invention has the effect of improving the low-temperature discharge
property of lithium primary batteries.

INDUSTRIAL APPLICABILITY

[0131]According to the present invention, there is provided a novel phenyl
sulfonate compound useful as intermediate materials for medicines,
agricultural chemicals, electronic materials, polymer materials and the
like, or as battery materials. Using the nonaqueous electrolytic solution
containing the phenyl sulfonate compound of the present invention brings
about lithium batteries excellent in low-temperature cycle property.